1. Field of the Invention:
The present invention relates to a paper sheet feeder for feeding a cut sheet such as paper into an apparatus which uses the cutting sheet, such as a copying machine, printing machine, etc.
2. Description of the Prior Art:
The cut sheets which are presently used for apparatus such as copying machines are different in their material quality, thickness, surface condition, etc., and the sheet feeder for feeding such sheets into the apparatus must be capable of properly feeding these different qualities of cut sheets.
A construction of the conventional sheet feeder for a copying machine is disclosed in Japanese Patent Publication (Unexamined) No. 56-64356/1981, according to which a cut sheet of paper is held up, pressed onto a feed-in roller, and under the rotating force of the feed-in roller conveyed by a frictional force into the copying machine. At this time, the pressing force exerted between the paper and the feed-in roller is generally produced by the recovery force of a spring. However, according to such construction, the pressing force varies because the recovery force of the spring varies depending on the size of the paper and the remaining number of sheets. Further, a motive power source which consumes additional energy is required to provide a torque for holding up the piled sheets of paper. Further, such an arrangement necessitates the use of cams and clutches. The increased number of parts leads to a higher cost.